Folded honeycombs known from WO 97/03816 are produced continuously from a single layer, e.g. a flat body. Hexagonal cells are constructed by folding after the introduction of cuts. The cells are bridged by covering-layer connecting surfaces. Folded honeycombs without cuts can be produced economically from one continuous layer of thermoplastic film by rotational vacuum thermoforming. Such folded honeycombs are described in WO 00/32382 and have connecting surfaces covering every hexagonal cell on both sides.